Thermal cracking of gaseous and liquid hydrocarbons to produce lighter weight materials such as olefins is well-known. In addition, the prior art has taught various methods for cooling high temperature gases produced in cracking furnaces. The cracked gases can be cooled either directly, by being quenched by a coolant, or indirectly, by passage through an indirect heat exchange zone, or can be partially cooled by direct cooling followed by indirect cooling. Although the indirect cooling method offers some advantages over the direct cooling method (the direct method adding, usually, extraneous material to the stream being cooled), the indirect cooling system does not prevent occurrence of coking in the path from the outlet of the pyrolysis reaction effluent conduit to the entrance of the indirect cooling device where the cracked gas will be cooled. The present invention is directed to an indirect heat exchange system wherein different sized tubes are used and are so-arranged that the flow of gases through all of the heat exchange tube in the indirect heat exchanger is substantially equalized, thereby preventing build-up of coke deposits at the inlets to the heat exchange tubes.
Accordingly, an object of this invention is to provide an improved heat transfer system wherein deposition of coke is minimized.
Another object of this invention is to provide a method of indirect cooling cracked gases whereby coke deposits in the heat exchanger are minimized.
A further object of this invention is to provide a method of pyrolyzing hydrocarbon feeds and cooling of the pyrolysis effluent in an indirect shell-tube heat exchange zone having a novel arrangement of tubular elements.
Other objects, aspects, as well as the several advantages of the invention will be apparent to those skilled in the art upon reading the specification, the drawings, and the appended claims.